Facultad de Ciencias Químicas Departamento de Ingeniería Química y de Materiales

Eva Sanz Santos, M. Larriba, V. I. Águeda, S. Álvarez-Torrellas, G. Ovejero, J. García

Application of sludge-based activated carbons for effective adsorption of neonicotinoid pesticides

Workshop REMTAVARES 2020

evsanz08@ucm.es

1. INTRODUCTION

Surface and ground water are highly contaminated An effective method is urgently required

Emerging and priority pollutants

Non biodegradable

Persistent

Conventional WWTP

High toxicity

1. INTRODUCTION

Bee decline

NegativeEnvironmental

Effects

Neonicotinoid pesticides are the most widely used insecticides in the world

Thiamethoxam (THM)Molecular volume: 303 Å3

Acetamiprid (ACT)Molecular volume: 266 Å3

Imidacloprid (IMD)Molecular volume: 271 Å3

1. INTRODUCTION

1. INTRODUCTION

In Spain, around 1.200.000 tons of sewage sludge (dry solid) are produced annually

↑ industrialization + ↑ urbanization = ↑ sludge production

Valorization

Activated Carbon

How to solve thisproblem?

Agricultural usage, landfilling or incineration are causing secondary pollution problems

2. EXPERIMENTAL METHOD

Synthesis of the activated carbons

Drying sludge

24h, 105°C

Impregnation

24h, room temperature

ZnCl2, FeCl3, Fe(NO3)3 and Fe2(SO4)3

Drying

24h, 105°C

Pyrolysis

800°C, 2h, N2 flow

Washing

1º) HCl 5M

2º) Deionized H2O

Drying

24h, 105°C

Pyrolysis

800°C, 2h, N2 flow

2. EXPERIMENTAL METHOD

Experimental adsorption tests

Operation conditions

Orbital shakerSolution volume: 25 mLRoom temperatureStirring speed: 250 r.p.m.Initial pesticide concentration: 50 mg L-1

Adsorbent particle size: 250-50 µm.Adsorbent load:

• Kinetic tests: 0.3 g L-1

• Equilibrium adsorption tests: 0.06 – 1.5 g L-1

3. RESULTS AND DISCUSSION

Characterization of the precursor: sludge

Sludge

Ultimate analysis (%)

C O H N P S Cl

47.89 6.84 6.62 3.38 1.18 0.49 1.13

Metal content (%)

Na Mg Al Si K Ca Ti Mn Fe Cu Zn Ni

0.15 0.02 0.38 0.17 0.49 7.25 0.02 0.01 0.19 0.01 0.02 0.03

Total solids (g/L) 56.76

Volatile solids(g/L) 46.24

Fixed solids(g/L) 10.52

COD(g O2/L) 55.36

Pharmaceutical industry sludge: Ercros Industrial, Aranjuez (Madrid)

80%

3. RESULTS AND DISCUSSION

Characterization of the activated carbons

Micro-mesoporous character of

activated carbons: N2 adsorption-desorption isotherms Type IV,according to IUPAC classification(Thommes, M. et al., 2015)

0,0 0,2 0,4 0,6 0,8 1,0

0

50

100

150

200

250

300

350

400

Adso

rbed V

olu

men (

cm³/

g)

Relative Pressure (P/P0)

AC-ZnCl2

AC-FeCl3

AC-Fe(NO3)3

AC-Fe2(SO4)3

Adsorbent SBET

(m2 g-1)Sext

(m2 g-1)VTotal

(cm3 g-1)VMicro

(cm3 g-1)VMicro/VTotal pHPIE

AC-ZnCl2 558 145 0.35 0.15 0.43 2.14AC-FeCl3 468 170 0.56 0.16 0.29 5.40

AC-Fe(NO3)3 240 158 0.32 0.04 0.13 6.81AC-Fe2(SO4)3 233 203 0.48 0.01 0.02 3.08

3. RESULTS AND DISCUSSION

Characterization of the activatedcarbons

AC-Fe(NO3)3 activatedcarbon has very strongmagnetic properties.

Very interesting as catalyst inheterogeneous Fenton processes (CWPO)=> FUTURE WORKDetermination of magnetic hysteresis loop

3. RESULTS AND DISCUSSION

Adsorption kinetics

0 20 40 60 80 100 120 140 160 180

0,0

0,2

0,4

0,6

0,8

1,0

C/C

0

Time (h)

ACT

THM

IMD

AC-ZnCl2

0 20 40 60 80 100 120 140 160 180

0,0

0,2

0,4

0,6

0,8

1,0

C/C

0

Time (h)

ACT

THM

IMD

AC-FeCl3

0 20 40 60 80 100 120 140 160 180

0,0

0,2

0,4

0,6

0,8

1,0

C/C

0

Time (h)

ACT

THM

IMD

AC-Fe(NO3)3

0 20 40 60 80 100 120 140 160 180 200

0,0

0,2

0,4

0,6

0,8

1,0

C/C

0

Time (h)

ACT

THM

IMD

AC-Fe2(SO4)3 Initial

Final

↑te ↑molecular volume

266 Å3 ≈ 271 Å3 < 303 Å3

ACT IMD THM

3. RESULTS AND DISCUSSION

Adsorption kinetics

Parameters

Adsorbent Pesticide te (h) qe (mg g-1)

AC-ZnCl2

ACT 24 84THM 144 97IMD 48 106

AC-FeCl3

ACT 48 70THM 144 66IMD 48 76

AC-Fe(NO3)3

ACT 96 66THM 144 135IMD 72 35

AC-Fe2(SO4)3

ACT 96 23THM 144 195IMD 72 22

AdsorbentSBET

(m2 g-1)

AC-ZnCl2 558AC-FeCl3 468

AC-Fe(NO3)3 240AC-Fe2(SO4)3 233

Generally, ↑SBET ↑qe

Adsorption + Reaction contributions in THM

removal

3. RESULTS AND DISCUSSION

Modelling of adsorption kinetics

Pseudo-first order model Pseudo-second order model

Adsorbent Micropollutant qe Exp.(mg g-1)

qe(mg g-1)

k1(min-1) R2 qe

(mg g-1)K2 x10-4

(g mg-1 h-1) R2

AC-ZnCl2

ACT 84.31 84.21 0.0047 0.8700 78.81 1.18 0.8670

THM 96.93 96.93 0.0233 0.8042 96.74 5.93 0.8403

IMD 105.71 105.71 0.0228 0.8242 105.01 4.92 0.8611

AC-FeCl3

ACT 70.06 70.04 0.0029 0.9290 65.09 0.65 0.9311

THM 66.09 66.09 0.0027 0.9688 93.81 1.80 0.8633

IMD 75.96 64.33 0.3789 0.9431 59.04 117.00 0.9639

AC-Fe(NO3)3

ACT 66.40 60.38 0.0004 0.9671 55.69 1.36 0.9418

THM 135.00 124.48 0.0003 0.9848 111.99 0.04 0.9646

IMD 35.42 35.41 0.0021 0.8870 33.04 0.91 0.8993

AC-Fe2(SO4)3

ACT 23.29 23.29 0.0046 0.8538 39.83 49.10 0.9332

THM 194.87 156.15 0.0002 0.9129 138.73 0.01 0.9040

IMD 21.54 21.54 0.0044 0.8886 64.45 4.25 0.9466

Pseudo-first order model

Pseudo-second order model

ln 𝑞𝑒 − 𝑞 = ln 𝑞𝑒 − 𝑘1 ∙ 𝑡𝑡

𝑞=

1

𝑘2 ∙ 𝑞𝑒2 +

𝑡

𝑞𝑒

3. RESULTS AND DISCUSSION

Adsorption isotherms

0 10 20 30 40 50

0

20

40

60

80

100

120

140

qe (

mg

/g)

Ce(mg/L)

ACT

THM

IMD

AC-Fe(NO3)3

0 10 20 30 40 50

0

20

40

60

80

100

120

140

160

180

qe (

mg

/g)

Ce (mg/L)

ACT

THM

IMD

AC-ZnCl2

0 10 20 30 40 50

0

20

40

60

80

100

120

140

q e (

mg/

g)

Ce (mg/L)

ACT

THM

IMD

AC-FeCl3

0 10 20 30 40 50

0

20

40

60

80

100

120

140

160

180

q e (

mg

/g)

Ce (mg/L)

ACT

THM

IMD

AC-Fe2(SO4)3

Adsorption isothermstype S3 and S4,according to Gilesand col. classification

Multilayer adsorption

3. RESULTS AND DISCUSSION

Modelling of adsorption isotherms

1

sat e

e

e

q b Cq

b C

=

+ Langmuir 1/ Fn

e F eq K C= Freundlich

Langmuir Freundlich

Adsorbent Pesticideqexp

(mg g-1)

qteor

(mg g-1)

qsat

(mg g-1)

b

(L mg-1)R2

qteor

(mg g-1)

KF

(L g-1)nF R2

AC-ZnCl2

ACT 128.94 112.94 886713 3.06 0.9555 115.32 1.98 0.92 0.9590

THM 126.76 149.45 899454 4.21 0.8755 126.25 59.16 4.85 0.9786

IMD 166.13 164.55 884860 4.24 0.9756 149.40 12.82 1.54 0.9728

AC-FeCl3

ACT 113.88 95.89 884860 2.58 0.8899 85.05 16.24 2.26 0.9226

THM 81.08 82.20 884860 1.72 0.8154 65.64 15.81 2.70 0.9501

IMD 104.09 103.61 884860 2.59 0.9604 92.33 11.71 1.85 0.9692

AC-

Fe(NO3)3

ACT 60.55 34.19 886713 0.81 0.7685 37.60 0.04 0.57 0.7930

THM 140.19 160.52 899455 4.81 0.6790 143.31 100.95 10.31 0.9318

IMD 55.82 39.04 884860 0.95 0.8998 42.64 0.06 0.59 0.9256

AC-

Fe2(SO4)3

ACT 60.55 34.19 884860 0.81 0.7685 37.09 0.06 0.60 0.7916

THM 140.19 160.52 899455 4.81 0.6789 143.31 100.95 10.31 0.9318

IMD 55.82 38.67 884860 0.94 0.8998 42.38 0.08 0.61 0.9254

4. CONCLUDING REMARKS

• Activated carbons show heterogeneous textural properties,characteristic of biomass-based activated carbons and maybeattributed to the heterogeneous character of sludge precursor.

• By using Fe(NO3)3 salt as an activating agent, an activatedcarbon with strong magnetic properties has been obtained.

• High adsorption capacity values have been obtained despite theslow adsorption kinetics, as a consequence of diffusional/sterichindrance effects.

• Generally, adsorption isotherms showed a bi-layer profile.

• For the removal of THM pesticide on AC-Fe(NO3)3 and AC-Fe2(SO4)3 activated carbons, two simultaneous contributions,e.g., adsorption and reaction, have been observed.

Thanks!

Contact:

Grupo de Catálisis y Procesos de Separación

Universidad Complutense de MadridWeb: www.ucm.es/gcypse-mail: evsanz08@ucm.es